Platypnea Orthodeoxia Syndrome of Intra-cardiac Etiology: A Case Report.

While the prevalence of patent foramen ovale (PFO) is well-established in the literature, the prevalence of platypnea orthodeoxia syndrome (POS), a rare cause of positional hypoxemia, requires further investigation. An 88-year-old woman presented with respiratory distress and was ultimately diagnosed with POS following multiple cardiac procedures that failed to identify a structural cause of her dyspnea. Outpatient evaluation of oxygen saturations in both sitting and supine positions in addition to supine echocardiography revealed a position-dependent PFO. The patient's hypoxemia then resolved with shunt closure. Echocardiography with micro-bubble studies as well as attention to filling pressures should therefore be performed with variation in the vertical axis to rule in POS in cases of dyspnea and hypoxemia of undetermined etiology.  PFO can cause intra-cardiac shunts that appear with changes in position and cause dyspnea via POS. It is ultimately important, however, to understand that not every PFO needs to be closed and that patients should be carefully selected for shunt closure when indicated by right heart hemodynamics.